Control means for the secondary induction passage of a two-stage carburetor



June 1, 1965 w. o. MANNING, JR

3,186,691 CONTROL MEANS FOR THE SECONDARY INDUCTION PASSAGE OF A TWO-STAGE CARBURETOR Filed May 25. 1961 2 Sheets-Sheet 1 INVENTOR.

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aw PAM/9 United States Patent ration of Michigan Filed May 25, 1961, Ser. No. 112,577 7 Claims. (Cl. 261-23) This invention relates to multi-stage carburetors, and more particularly to means for controlling the secondary induction passages of a two-stage carburetor or of a multiple carburetor assembly such as a three carburetor arrangement.

Many internal combustion engines, particularly those employed to drive motor vehicles, are equipped with a so-called automatic choke, the main purpose of which is to control the primary induction passages so as to provide a relatively n'ch fuel-air mixture for the engine on cold starting and until the engine has reached normal operating temperature. A common type of automatic choke, for example, is that having an offset choke plate pivoted in the primary induction passage upstream of the main fuel nozzle, a vacuum piston responsive to engine manifold vacuum or initially opening the choke plate on starting the engine and a thermostatic coil spring to resist such initial opening, with the resistance of the coil spring progressively decreasing as the engine warms up to normal engine temperature.

The throttles in the secondary induction passages of a two-stage carburetor may be either manually or automatically operated. In either case, they are controlled to open when the capacity of the primary induction passages is exceeded. In order to retain the enrichment effect of the automatic choke, it is sometimes the practice to mechanically prevent the opening of the secondary throttles, regardless of the position of the primary throttles, until a certain engine temperature is reached or until the automatic choke has reached a particular degree of opening.

Whether the secondary throttles are mechanically or automatically operated, the opening thereof greatly reduces the manifold vacuum acting on the primary and secondary idle and transfer fuel systems; this may also reduce the velocity of the air flow through the primary and/or secondary venturis, in which case it would reduce the venturi vacuum acting on the main fuel nozzles. This being so, the opening of the secondary throttles almost always causes a leaning-out of the fuel-air mixture supplied to the engine and a consequent so-called dead spot noticeable to the vehicle operator.

In-single barrel type carburetors, all of the air passes through a single venturi, thereby providing sufficient operating vacuum. In a multi-barrel type carburetor, however,- the air required for engine operation is divided to pass through four venturis; consequently, the operating vacuum available at low air flows is reduced. That is, the present type four barrel carburetors do operate reasonably well at high air flows, but efliciency is somewhat lacking at low air flow demands.

It is now proposed to provide a valve to control the air passing through the secondary induction passages.

'Such a'valve will provide a choking action on the second- "ice eliminate the need of the above referred to secondary throttle lock-out provided during cold operation.

A further object of this invention is to locate anywhere above the main fuel nozzle in the secondary induction passage an automatically-operated air valve to provide a choking action on the secondary airinduction system of a carburetor. Actuation of this air valve may be accomplished, just for example, by a rod connected to a diaphragm which in turn is actuated by vacuum from the primary and the secondary venturi. The opening of such a valve would preferably be calibrated to lag behind the opening of the secondary throttle plates, and with the actuating mechanism referred to above, the time and rate of the opening of the valve could be varied by varying the size of the vacuum pick-up, the design of the operating linkages and the force and rate of the diaphragm return spring.

A further object of this invention is to provide an air valve which will at times allow little or no air to pass through the secondary induction passages, even though the secondary throttles have opened to some extent during acceleration. This will allow vacuum from the engine intake manifold to cause some fuel flow from the secondary fuel systems and cause a desirable enrichment of the fuel-air mixture during acceleration.

Other objects and advantages will become more apparent as the descripton proceeds, especially when taken in consideration with the accomanying drawings, where- FIGURE 1 is a side elevational view, with portions thereof cut away and in cross section of a multi-barrel type carburetor embodying the invention;

FIGURE 2 is a fragmentary view showing a first modification; 7

FIGURE 3 is a fragmentary view showing a second modification.

Referring to the drawings in greater detail, a carburetor 10 is formed to provide a primary air intake portion 12 and'a secondary air intake portion 14, the throttle body portion 16 being mounted to the engine manifold 18.

The primary choke plate 28 mounted on shaft 26 has fixed thereto lever 24; the automatic choke control assembly 20 actuates choke plate 28 through link 22 in usual and well-known manner.

A primary fuel discharge nozzle 30 located in the venturi portion 34 of the air intake portion 12 is supplied by suitable fuel conduits communicating with fuel bowl 31. The usual primary idle and transfer (low speed) fuel outlet port 32 also connects to fuel bowl 31. As is well understood in the art, manifold vacuum causes fuel to be discharged through the port 32 at idle and intermediate speeds, and vacuum in the throat of the venturi 34 causes fuel to be discharged from the main nozzle 30;

The throttle body portion 16 of the carburetor 10 is provided with a primary throttle plate 48 mounted on a shaft 46 having fixed thereto a lever 44. A control rod '36, which is manually operated, actuates a three-way .The lower portion of lever 54 connects through a link 58 withthe end of lever 60 fixed to shaft '62, the secondary throttle plate 64 being mounted on'shaft 62 in any suitable manner.

The secondary fuel discharge nozzle 68 located in the venturi 66 of air intake portion14 is of course connected to a secondary fuel bowl 67 by means of conduit 70'and metering restriction 72. Conduit 76connects the idle restriction 74 to the idle and transfer port 78. The secondary fuel systems briefly described above are, of course, essentially the same as the equivalent primary fuel systems.

The carburetor structure described above, for purposes 7 90 positioned between housing 92 and the diaphragm 88 will normally exert a force on rod 86 and the lever 84 to rotate shaft 82 counterclockwise so as to close valve 80.

The chamber formed by cover 94 and diaphragm 88 is vented to atmosphere by means of part 94'. The suction chamber 96 formed by housing 92 and diaphragm 88 communicates by means of conduits 98 and 100 with passage 102 which is open at the ends thereof to venturis 34 and 66.

The first modification shown by FIGURE 2 illustrates anotherwell known type of carburetor wherein the secondary throttle plate 64 is operated by a vacuum diaphragm assembly 110 mounted on the carburetor in any suitable manner. Actuating rod 112 is anchored at one end to the diaphragm of diaphragm assembly 110, and

its other end is pivotedly connected to the lever 60 secured to shaft 62 so as to actuate secondary throttle plate 64. A

conduit 114 connects the, suction chamber of diaphragm assembly 110 with conduit 120 leading to the primary and secondary venturi vacuum pickups 118 and 116, IESPBC'.

tively. The vacuum-operated secondary throttle valve 64 operates in a manner generally similar to the operation of the manually-operated throttle valve 64 shown by FIG- URE 1, except that instead of a mechanical connection the secondary throttle opens when the primary venturi vacuum reaches a value indicative of an open primary throttle. 7

The modificationshow'n on FIGURE 3 is similar to that shown by FIGURE 2, except that the vacuum di-' aphragm assembly 110 is responsive only to vacuum from the primary venturi vacuum sensed at 118 and transmitted by means of conduit 122.

Operation In all cases, the 'air valve 80 is normally closed and remains closed during engine cranking and idle operation, as well or during the initial part throttle operation. This is, of course, also true of the secondary throttle 64, regardless of the means of actuation thereof. Preferably, the valve 80 will begin to open when the air passing through the venturi 34 creates enough vacuum to first open the secondary throttle 64 and then begin to actuate the 'diaphragm 88. When the venturi vacuums increase sufficiently, the air valve 80 will remain fully open. As already stated, the timing or the operation of the air valve SOand the secondary throttle 64 may be varied by varying'the design details. Possibly orifice 66 is not needed in some cases. a

In view of the lag in operation, as, between air valve 80 and throttle valve 64, it is apparentthat the air valve 80 will limit or prevent air from passing through the secondary induction passage 14, even during acceleration at lower air flow. With the secondary valve stlclosed or partially closed, vacuum in engine manifold 18 will pro essary for smooth and efficient engine operation.

made within the scope of the appended claims.

What I claim as my invention is:

1. A carburetor comprising a body having primary and secondary induction passages formed therein, each of said passages having a venturi restriction and a throttle valve pivotally mounted downstream of said venturi, a choke valve pivotally mounted in said primary induction passage upstream of said venturi therein, and an air valve pivotally mounted in said secondary induction passage upstream of said venturi therein, and means operably connected to said air valve for controlling said air valve in said secondary induction passage in response to air flow through said primary and said secondary venturi.

2. .A carburetor comprising a body having primary and secondary induction passages formed therein, each of said passages having a venturi restriction and a throttle valve pivotally mounted downstream of said venturi, a choke valve pivotally mounted in said primary induction passage upstream of the venturi therein, and an air valve pivotally mountedin said secondary induction passage upstream of the venturi therein, and means operably connected to said air valve for controlling said air valve in said secondary induction passage in response to air flow through said primary venturi.

3. An internal combustion engine with an inlet manifold and having primary air induction passages and at least one secondary induction passage, each of such passages being formed with a venturi restriction therein and having a throttle valve pivotally mounted downstream of said venturi, each of said induction passages also having separate idle and main fuel supply systems associated therewith, means for opening said secondary throttle after said primary throttle has opened a predetermined amount, a choke valve pivotally mounted in said primary induction passage upstream of said venturi, an 'air valve pivotally mounted in said secondary induction passage upstream of said venturi, and additional means operably connected to said air valve to retain said air valve in a closed position for a predetermined time after said secondary throttle valve has opened for inducing fuel flow through said fuel supply systems in said secondary induction passage in response to engine inlet manifold vacuum said last mentioned means including a passageway communicating with said primary venturi.

4. In a two-stage carburetor having primaryand secondary induction passages, each of said passages having a throttlevalve and a venturi restriction therein, and a choke valve pivotally mounted in said primary induction passage upstream of said venturi, an air valve pivotally mounted in said secondary induction passage upstream of said venturi, a pressure responsive device operably connected to said air valve, resilient means foiuaiasing said pressure responsive means in a direction so' as to close said air valve, a first conduit communicating between said primary and said secondary venturies and a second conduit communicating between said first conduit and said pressure responsive device.

5. In a two-stage carburetor having primary and secondary induction passages, each of said passageshaving a throttle valve and a venturi restriction therein, and a choke valve pivotally mounted in said primary induction passage upstream of said venturi, an air valve pivotally mounted in said secondary induction passage upstream of said venturi, a pressure responsive device operably connected to said. air valve, resilient means for biasing said pressure responsive means in a direction so' as to close said air valve, and a conduit communicating between said 7 primary venturi and said pressure responsive means. 7

6.1m a two-stage carburetor having primary and secondary'induction passages, each of said passages having a '70 vide increased fuel flow through the. secondary fuel sys- .tems, thus enriching the total fuel-air'mixture that is necthrottle valve and a venturi restriction therein, and a choke valve pivotally mounted in said primary induction passage upstream of said venturi, an air valve pivotally' mounted in said secondary induction passage upstream of said venturi,'a first pressureresponsive device operably connected to said air valve, resilient means for biasing said first pressure responsive means in a direction so as to close said air valve, a first conduit communicating between said primary venturi and said first pressure responsive means, a second pressure responsive device operably connected to said secondary throttle valve and a second conduit communicating between said primary venturi and said second pressure responsive means.

7. In a two-stage carburetor having primary and secondary induction passages, each of said passages having a throttle valve and a venturi restriction therein, and a choke valve pivotally mounted in said primary induction passage upstream of said venturi, an air valve pivotally mounted in said secondary induction passage upstream of said venturi, a first pressure responsive device operably connected to said air valve, resilient means for biasing said first pressure responsive means in a direction so as to close said air valve, a first conduit communicating between References Cited by the Examiner UNITED STATES PATENTS 2,162,05 6 6/39 Bracke. 2,452,698 11/48 Strebinger. 2,832,576 4/58 Henning.

HARRY B. THORNTON, Primary Examiner.

RONALD R. WEAVER, EUGENE F. BLANCHARD,

Examiners. 

2. A CARBURETOR COMPRISING A BODY HAVING PRIMARY AND SECONDARY INDUCTION PASSAGES FORMED THEREIN, EACH OF SAID PASSAGES HAVING A VENTURI RESTRICTION AND A THROTTLE VALVE PIVOTALLY MOUNTED DOWNSTREAM OF SAID VENTURI, A CHOKE VALVE PIVOTALLY MOUNTED IN SAID PRIMARY INDUCTION PASSAGE UPSTREAM OF THE VENTUREI THEREIN, AND AN AIR VALVE PIVOTALLY MOUNTED IN SAID SECONDARY INDUCTION PASSAGE UPSTREAM OF THE VENTURI THEREIN, AND MEANS OPERABLY CONNECTED TO SAID AIR VALVE FOR CONTROLLING SAID AIR VALVE IN SAID SECONDARY INDUCTION PASSAGE IN RESPONSE TO AIR FLOW THROUGH SAID PRIMARY VENTURI. 